Photo-luminescent pigment application

ABSTRACT

A method of applying photo-luminescent pigment to a substrate, such as an aluminum or metal strip containing channels or depressions, includes preparing a dry powder formulation comprising a photo-luminescent pigment and a carrier/fixer, depositing the dry powder formulation onto the substrate surface, and heating to fuse the dry powder formulation to the substrate surface. The photo-luminescent pigment can be applied using an apparatus which includes a hopper adapted to contain the dry powder formulation, one or more orifices adapted to allow transfer of the dry powder formulation from the hopper to a substrate surface and a guide rail system for locating the substrate surface in both a fixed horizontal plane and a fixed vertical plane below the hopper and orifice.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a method and apparatus for applyingphoto-luminescent pigment to a substrate surface, more particularly forapplying photo-luminescent pigment to aluminum or other metal stripsused, for example, as stair nosings. The invention also relates to aproduct-produced by said method and apparatus.

[0003] 2. Background to the Invention

[0004] Low level floor or walkway lighting is commonly used in suchplaces as picture theaters, sports arenas and aircraft as both acourtesy and safety feature for patrons or passengers. This lightingoften takes the form of an electrical or electronic lighting means in oron the floor along either side of a walkway or across the nosing ofstairs. Low level floor lighting is particularly important in picturetheaters and sports arenas where patrons may be required to negotiatesteps in aisles when only low levels of ambient light are present, or instairwells of buildings during an emergency when there may be failure ofthe main lighting source.

[0005] Known methods of floor lighting using electrical or electronicmeans have a disadvantage because they require electrical wiring to berun to areas where access for the wiring may be limited. They are alsoprone to failure during failure of the main power supply. Additionally,the electronic lighting means are often of a low voltage type requiringsome form of voltage reduction means such as an inverter, converter, ortransformer. Not only does addition of this equipment add to thecomplexity and cost of the installation but also provides for additionalmodes of failure.

[0006] It is known to apply a photo-luminescent pigment to a rope, tapeor fabric. This photo-luminescent pigment is stimulated by visible lightand remains luminescent for a considerable period after the light sourceis removed. The problem with tape or fabric impregnated with pigment isthat lacks durability for heavy wear areas such as walkways or stairs.

[0007] Photo-luminescent pigment has been sprayed onto more durablesubstrate surfaces such as aluminum or metal strips or extrusions. Oncethe spray has dried, it is ground to provide a smooth finished surface.This overcomes the abovementioned problems associated with heavy wearareas, but considerable pigment is wasted during the spraying andgrinding process.

[0008] Accordingly it is an object of the present invention to provide amethod and apparatus for applying photo-luminescence pigment to asubstrate which avoids or overcomes some of the abovementioneddisadvantages, or which at least provides the public with a usefulchoice.

SUMMARY OF THE INVENTION

[0009] According to a first aspect of the invention there is provided amethod of applying photo-luminescent pigment to a substrate, said methodincluding:

[0010] preparing a dry powder formulation comprising, at least, aphoto-luminescent pigment and a carrier/fixer;

[0011] depositing the dry powder formulation onto a substrate surface;

[0012] heating the dry powder formulation to fuse it to the substratesurface.

[0013] Preferably the substrate surface has depressions or channelsadapted to receive the dry powder formulation.

[0014] Preferably a light reflecting layer is applied to the substratesurface before depositing the dry powder formulation.

[0015] Preferably the volume ratio of photo-luminescent pigment tocarrier/fixer in the dry powder formulation is such that the fusedmaterial exhibits substantially the same strength and durabilityproperties of the carrier/fixer, while still exhibiting thephoto-luminescent properties of the pigment. More preferably the volumeratio is substantially in the range of 1% to 35% photo-luminescentpigment to carrier/fixer.

[0016] Preferably the dry powered formulation may be heated to between,substantially, 160 to 210 degrees centigrade, or to a temperaturerecommended by the manufacturer of the carrier/fixer, for approximately10 to 20 minutes or until the formulation is molten. The moltenformulation may be cooled after heating.

[0017] Preferably the carrier/fixer is a heat curable polymer.

[0018] Preferably the dry powder formulation may include smallquantities of additives, such as a de-gassing additive, to ensure asmooth surface finish.

[0019] Preferably the substrate is stamped, extruded or milled aluminumor metal.

[0020] According to a second aspect of the invention there is providedan apparatus for applying photo-luminescent pigment to a substrate, saidapparatus including:

[0021] a hopper adapted to contain a dry powder formulation;

[0022] one or more orifices adapted to allow transfer of the dry powderformulation from the hopper to a substrate surface;

[0023] a guide rail system for locating the substrate surface in both afixed horizontal plane and a fixed vertical plane below the hopper andorifice; and

[0024] a heat-curing system for providing enough heat to turn the drypowder formulation into a molten mix.

[0025] Preferably the apparatus also includes a cooling system to coolthe molten mix.

[0026] Preferably the apparatus also includes a drive system to move thesubstrate through the apparatus.

[0027] Preferably the apparatus includes a support roller mounteddirectly beneath the orifice(s) and hopper to support the substrate.

[0028] Preferably the apparatus includes an adjustable mounting bracketadapted to enable the hopper to be located in the correct position sothat the orifice(s) lines up with the substrate.

[0029] Preferably the orifice is adapted to communicate snugly with thesubstrate surface such that the dry powder formulation is depositedsubstantially only where required.

[0030] Preferably the apparatus includes a mechanism for tapping orshaking the hopper so that any voids in the dry powder formulation arere-filled.

[0031] Preferably the apparatus includes a brush mounted below theroller, and with its bristles in contact with the roller, so that anypowder that falls onto the roller is subsequently brushed off.

[0032] The heat-curing system may be an oven. Optionally, theheat-curing system may be a continuous oven process, and in oneembodiment may include infra-red heating elements.

[0033] Preferably the apparatus includes an automatic loading andunloading means at each end thereof.

[0034] The invention also provides for a product when produced accordingto the process, or by an apparatus, herebefore defined.

[0035] Further aspects of the invention will become apparent from thefollowing description which is given by way of example only.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above-mentioned and other features and advantages of thisinvention, and the manner of attaining them, will become more apparentand the invention will be better understood by reference to thefollowing description of an embodiment of the invention taken inconjunction with the accompanying drawings, wherein:

[0037]FIG. 1 illustrates a perspective cross section view through ahopper according to the invention; and

[0038]FIG. 2 illustrates an elevation view of the hopper and a feedtable; and

[0039]FIG. 3 illustrates a schematic overview of one embodiment of anapparatus according to the invention.

[0040] Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplification set out hereinillustrates one preferred embodiment of the invention, in one form, andsuch exemplification is not to be construed as limiting the scope of theinvention in any manner.

DESCRIPTION OF THE INVENTION

[0041] The invention provides for a method and apparatus for applyingphoto luminescent pigment, which is stimulated by UV and visible lightand will remain illuminated for a period after the light source isremoved, to a substrate such as aluminum or metal strips. The resultingsubstrate can be used to provide floor, stair or other courtesy oremergency lighting in public areas.

[0042] The process involves filling depressions or channels in asubstrate material (typically, but not exclusively, an aluminumextrusion or stamped or milled sheet of aluminum) with a dry powderformulation that contains a photo luminescent pigment; a carrier/fixer(typically a heat curable polymer); and preferably small quantities ofadditives (such as a flow additive and/or de-gassing additive) thatimprove the melt properties of the mix and ensure a smooth surfacefinish. Sufficient heat is applied to the combined formulation to meltand cure it, and when cooled it fuses to itself and to the substrate.

[0043] In order to improve the effectiveness of the photo-luminescentformulation a light reflective layer can be applied to the substratebefore depositing the formulation.

[0044] The depressions or channels in the substrate are filled up withthe dry powder formulation to be level with the top surface of thesubstrate material. When the formulation becomes molten the air betweenthe particles is expelled and the subsequently fused material forms athick film that smoothly covers both the horizontal and verticalsurfaces of the depressions or channels in the substrate. Because thesurface of the fused formulation is lower than the highest point of thedepressions or channels it is protected from wear and is suited to usein floor illumination situations.

[0045] While a number of products suitable for such a photo-luminescentformulation may be apparent to a skilled artison, the products used inthe current invention are LUMINOVA, a photo-luminescent pigment fromNemoto Japan; and TPE, a carrier/fixer produced by Dulux New Zealand.The flow and de-gassing additives are also produced by Dulux NewZealand.

[0046] The ratio of photo-luminescent pigment to carrier/fixer in thedry powder formulation is dependent on the intensity and duration ofillumination desired. If greater intensity and duration of illuminationis desired, more pigment is added. A typical formulation will containbetween 30% and 60% photo luminescent pigment powder by weight. However,because the specific gravity of the powder is typically 3-4 timesgreater than the rest of the dry powder formulation, the photoluminescent pigment volume ratio is typically in the range 10% to 30%.

[0047] Because the photo-luminescent pigment makes up a relatively smallpart of the total volume of the fused material the fused materialexhibits substantially the same strength and durability properties thatthe carrier/fixer would have without the inclusion of the photoluminescent pigment, but it also has the added property of beingphoto-luminescent. Success has been achieved with volume ratios between1% and 35% photo-luminescent pigment.

[0048] The principle of the process is to pass the substrate material,with the channels or depressions facing upwards, below a hopper which isfilled with the dry powder formulation. The hopper has one or morebottom orifices which is shaped so that the dry powder formulation willfall under its own weight into the channels or depressions and will notspill on either side of the substrate. As the substrate passes under thehopper the lower surface of the bottom orifice(s) wipe the top surfaceof the substrate material clean so that the only dry powder formulationthat is removed from the hopper is that which fills the channels ordepressions. The channels or depressions are filled to be level with thetop surface of the substrate. Heat is then applied to cure the drypowder formulation. After heating, the formulation may be cooled.

[0049] Individual pieces of the substrate material are successivelypassed underneath the hopper in such a way that no substantialquantities of the dry powder formulation fall between the tail end ofone piece and the lead edge of the subsequent piece.

[0050]FIGS. 1 and 2 illustrate, in detail, the hopper section 10 of anapparatus for applying photo luminescent material to a substrate. FIG. 3illustrates a schematic overview (not to scale) of the whole apparatus,each aspect of which will now be described.

[0051] The apparatus includes a guide rail system 8 for locating theindividual substrate pieces, in this case aluminum extrusion 1, in botha fixed horizontal plane and a fixed vertical plane.

[0052] A drive system is used to push individual substrate pieces passed(below) a hopper 2. This drive system may be a human operator, or it maybe a system of motorised rollers 11 that engage with one or two faces ofthe individual substrate pieces. Also, support roller 3 may be motorisedto drive the extrusion 1 below hopper 2. In an automated embodiment ofthe apparatus the motorised rollers 11 and 3 may be operated from avariable speed motor drive which may interface with a controller.

[0053] The hopper section 10 comprises the hopper 2, preferably withsteep sides to avoid build-up of product, that might hold typically, butnot exclusively, 1 to 1.5 kg of dry powder formulation. The hopper 2shown in FIG. 1 is cut-away for illustration purposes.

[0054] An adjustable mounting bracket 4 may also be included to enablethe hopper 2 to be located in the correct position so that a bottomorifice 5 lines up with the channels or depressions 6 in the extrusion1. Orifice 5 may be formed in a die 9, which is adapted to suit theextrusion 1 being used. The die 9 would abutt snugly over extrusion 1 sothat no formula was spilled or wasted. Various dies may beinterchangeable to provide for different substrates. The dies may havemore than orifice—for example a two orifice die for a two channel ordepression substrate.

[0055] There is a compressible foam rubber insert 7 between the hopperbody 1 and the bottom orifice 5, which suspends the bottom orifice 5 insuch a way that it will still seal against the extrusion 1 even if theextrusion 1 is not perfectly lined up with the hopper 2.

[0056] A support roller 3 mounted directly beneath the bottom orifice 5of the hopper 2 to support the extrusion 1 without imposing excessivefriction. This allows the extrusions 1 to be readily moved through thesystem. Roller 3 may be motorised but this is not essential as its mainfunction is to hold the extrusion up to the orifice 5. A bristle brush(not shown) may be mounted directly below the roller 3, with itsbristles in contact with the roller, so that any powder that falls ontothe roller is subsequently brushed off and will not to build up on theroller 3.

[0057] A mechanism (not shown) for tapping the hopper 2 at regularintervals can be provided so that any voids in the dry power arere-filled. Typically the tapping action will occur once every 30-60seconds of operation, which is not enough to allow the differentcomponents of the dry powder formulation to separate substantially. Inits simplest form this “mechanism” may in fact be the hand of a humanoperator, but ideally this function is carried out by a solenoid or airactuated arm. Alternatively an auger. or screw may be included whicheither continuously or intermittently “mixes” the formula, therebyfilling any voids.

[0058] The apparatus also includes a heat-curing system, for example anoven, 12 to provide enough heat to melt and cure the dry powderformulation, and bond it to the substrate. This could be an oven with arack system. After the individual substrate pieces have had theirchannels or depressions filled with the dry powder formulation they areloaded by hand onto the racks. When the racks are full the racks areplaced in the oven for the required time. Using this system a typicalcuring cycle may be 10 to 20 minutes at 160° C. to 200° C.

[0059] In an automated apparatus the oven would most preferably be acontinuous tunnel process so that after the individual substrate pieceshave had their channels or depressions filled with the dry powderformulation they immediately enter a curing tunnel 12 that rapidly heatsthem to typically 160° C. to 200° C. for a sufficient time to turn thedry powder formulation into a molten mix and bond it to the substrate.The individual substrate pieces then emerge from the opposite end of thetunnel. A cooling tunnel 13 may also be provided.

[0060] The curing tunnel could be either a hot-air type oven or aninfra-red oven. At present the applicant has found that the hot-air typeoven produces the best result. However, infra-red ovens provide a muchfaster and more direct heating method. The problem with infra-red ovensis that the rapid localised heating causes distortion of the substratematerial. The degree of distortion is dependent on the form and type ofsubstrate material. It is envisaged that with improvements in infra-redheating technology and substrate materials this will become thepreferred method.

[0061] The above-described system may be fully automated if required bythe use of automatic loading and unloading magazines at each end, 14 and15 respectively, of the production line 8. Automation of such a system,using for example a programmable logic controller or PC based controlsystem, is well within the capability of one skilled in the art and willnot be discussed further.

[0062] The photo-luminescent pigment application process will now bedescribed, by way for example only, to illustrate the method of theinvention.

[0063] A representative piece of substrate is placed on the guide railclose to the empty hopper, then passed into the gap between the bottomorifice of the hopper and the support roller. The position of the hopperassembly is adjusted as necessary to ensure that the bottom orificelines up with the channels or depressions in the substrate, and thereare no gaps to either side that would let powder escape. The hopper isthen filled with a thoroughly mixed quantity of the dry powderformulation.

[0064] The first piece of “production” substrate is then placed on theguide rail, immediately behind the representative piece of substrate,and moved towards the hopper assembly. In this way it pushes therepresentative piece of substrate through and passed the hopper assemblyand onto the guide rail on the other side of the hopper assembly. Therepresentative piece of substrate can subsequently have the powder thathas been applied to it removed by a vacuum cleaning head and then thesubstrate can be reused as a plug for the hopper's bottom orificewhenever production is halted.

[0065] Before the first piece of production substrate is pushed rightthrough the hopper assembly the second piece of production substrate ispicked up off a magazine and placed on the guide rail immediately behindthe first piece of production substrate. Once the first piece ofproduction substrate is away from the hopper assembly it can be takenoff the guide rail and placed on racks ready for oven curing.

[0066] The above step is then repeated until the oven racks are full.The racks are placed in the oven for the required curing cycle, thenremoved from the oven and allowed to cool before final inspection andpackaging.

[0067] At regular intervals, as required, the hopper is tapped to removevoids in the powder and the hopper is refilled with thoroughly mixed drypowder formulation.

[0068] When the production run has finished the representative piece ofsubstrate can be reused as a plug for the hopper's bottom orifice andfinally any left-over powder can be removed from the hopper.

[0069] It can readily be seen that whereas the above descriptiondescribes the method of operation for a non-mechanised form of theapparatus the process can readily be automated using the optionalautomating equipment described above so that the process becomes eithersemi-automatic or fully automatic. Such automation would be well withinthe capabilities of the nominally skilled person.

[0070] Photo-luminescent formulation can be applied, by theabove-described method, to articles having channelled surfaces for usein such places as picture theaters, sporting arenas, aircraft aisles andbuilding corridors/stairways where the illumination can be adapted inguiding people to an exit in an emergency or when normal lighting fails.Two examples of articles are step nosings and handrails.

[0071] A step nosing is the angled member across the front edge of astep. The current invention can be used to deposit photo-luminescentformulation within castellations, or recessed channels, in the topsurface of a step nosing. This results in a step nosing which isluminescent for an extended period after ambient illumination isswitched off, and hence helps maintain the safety of spectator areas inpicture theaters, sporting arenas and the like in low light situations.The extrusion 1 illustrated in FIG. 1 is a step nosing withcastellations, or recessed channels, 6 in its top surface.

[0072] In a further embodiment the photo-luminescent formulation mightbe deposited within castellations, or recessed channels, of a insertstrip which engages with the top surface of a step nosing. This wouldallow the photo-luminescent insert strip to be replaced withoutreplacing the whole step noising.

[0073] Photo-luminescent formulation could also be deposit withincastellations, or recessed channels, on stair and other handrails. Thecastellations, or recessed channels, carrying the photo-luminescentformulation may be part of a replaceable insert strip.

[0074] Where in the foregoing description reference has been made tointegers or elements having known equivalents, then such equivalents areherein included as if individually set forth.

[0075] Particular examples of the invention have been described and itis envisaged that improvements and modifications can take place withoutdeparting from the scope of the appended claims.

[0076] While this invention has been described as having a preferreddesign, the present invention can be further modified within the spiritand scope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

What is claimed is:
 1. A method of applying photo-luminescent pigment toa substrate, said method including: preparing a dry powder formulationcomprising, at least, a photo-luminescent pigment and a carrier/fixer;depositing the dry powder formulation onto a substrate surface; andheating the dry powder formulation to fuse it to the substrate surface.2. A method as claimed in claim 1 wherein the substrate surface has oneof a depression or channel adapted to receive the dry powderformulation.
 3. A method as claimed in claim 2 which further includesapplying a light reflecting layer to the substrate surface beforedepositing the dry powder formulation.
 4. A method as claimed in claim 1wherein the volume ratio of photo-luminescent pigment to carrier/fixerin the dry powder formulation is such that the fused material exhibitssubstantially the same strength and durability properties of thecarrier/fixer while still exhibiting the photo-luminescent properties ofthe pigment.
 5. A method as claimed in claim 4 wherein the volume ratiois substantially in the range of 1% to 35% of photo-luminescent pigmentto carrier/fixer.
 6. A method as claimed in claim 1 wherein the drypowered formulation is heated to a temperature recommended by themanufacturer of the carrier/fixer until the formulation is molten.
 7. Amethod as claimed in claim 6 wherein the formulation is heated tosubstantially between 160 to 210 degrees centigrade.
 8. A method asclaimed in claim 6 wherein the formulation is heated for approximately10 to 20 minutes.
 9. A method as claimed in claim 1 wherein afterheating the formulation is cooled.
 10. A method as claimed in claim 1wherein the carrier/fixer is a heat curable polymer.
 11. A method asclaimed in claim 1 wherein the dry powder formulation includes smallquantities of additives to ensure a smooth surface finish.
 12. A methodas claimed in claim 1 wherein the substrate is one of stamped, extrudedand milled metal.
 13. An apparatus for applying photo-luminescentpigment to a substrate having a surface, said apparatus including: ahopper adapted to contain a dry powder formulation, said hopper havingat least one orifice adapted to allow transfer of the dry powderformulation from the hopper to a substrate surface; and a guide railsystem for locating the substrate surface in both a fixed horizontalplane and a fixed vertical plane below the hopper and orifice; and aheat-curing system for providing enough heat to turn the dry powderformulation into a molten mixture.
 14. An apparatus as claimed in claim13 which also includes a cooling system to cool the molten mixture. 15.An apparatus as claimed in claim 13 which includes a drive system tomove the substrate through the apparatus.
 16. An apparatus as claimed inclaim 13 which includes a support roller is mounted directly beneathsaid orifice and said hopper to support the substrate.
 17. An apparatusas claimed in claim 13 which includes an adjustable mounting bracketadapted to enable the hopper to be located in the correct position sothat said orifice aligns with the substrate.
 18. An apparatus as claimedin claim 13 wherein said orifice is adapted to communicate snugly withthe substrate surface such that the dry powder formulation is depositedsubstantially only where required.
 19. An apparatus as claimed in claim13 which includes a mechanism for tapping the hopper so that any voidsin the dry powder formulation are re-filled.
 21. An apparatus as claimedin claim 13 wherein the heat-curing system is an oven.
 22. An apparatusas claimed in claim 13 wherein the heat-curing system is a continuousoven process.
 23. An apparatus as claimed in claim 21 wherein the ovenincludes infra-red heating elements.
 24. An apparatus as claimed inclaim 13 which includes an automatic loading means and automaticunloading means at each respective end of said guide rail system.
 27. Asubstrate bearing photo luminescent material when prepared using amethod according to claim
 1. 28. A substrate bearing photo luminescentmaterial when prepared using an apparatus according to claim
 13. 29. Astep nosing bearing photo luminescent material prepared using a methodaccording to claim
 1. 30. A step nosing bearing photo luminescentmaterial prepared using an apparatus according to claim
 13. 31. Ahandrail bearing photo luminescent material prepared using a methodaccording to claim
 1. 32. A handrail bearing photo luminescent materialprepared using an apparatus according to claim 13.